Lubricating oils



Patented Feb. 13, 1945' LUBRICATING OILS Elmer W. Cook, New York, N. Y.,and William D. Thomas, Jr., Stamford, Conn., assignors to AmericanCyanamid Company, New York, N. Y.,- a corporation of Maine No Drawing.Application November 13, 1941, Serial No. 419,016

6 Claims.

This invention relates to lubricating oils, particularly'those of thetype known as crankcase oils. Although the improved lubricating oils ofthe present invention are highly desirable for use in the crankcases ofpassenger automobiles, they are especially valuable for heavy dutyservice in truck, bus, aeroplane, marine and Diesel engines whichoperate for long periods of time at high temperatures. I

The principal objects of the invention are to provide an improvedlubricating oil of the heavy duty type which is particularly resistantto sludge formation and oxidation, being non-corrosive to alloy bearingsand other metal parts under conditions of extreme service, and which isfree from varnish formation and ring sticking tendencies.

In our copending application Serial No. 401,960, filed July 11, 1941,and in our copending'application Serial No. 415,411 filed October 17,1941, we have disclosed that hydrocarbon lubricating oils having greatlyimproved detergent, anti-corrosive and anti-sludge forming propertiesmay be prepared by the incorporation therein of minor amounts of variousdithiophosphates. While the lubricating oils containing these organicsubstituted dithiophosphates are extremely resistant to sludge formationunder conditions of heavy duty service we have found that when preparingthese improved lubricating oils from ordinary classes of lubricatingoils not highly refined a small amount of sludge will form when the oilis subjected to high temperatures for long periods of time in thepresence of air or oxygen. With the more highly refined oils such asthose treated by the solvent refining process the amount of sludgeformed under such conditions is very small. Since it is desirable,however, to use a lower cost oil in trucks, buse's, Diesel engines, etc.which operate almost continuously at high temperatures a furtherimprovement in lubricating oils reflned by conventional methods isdesirable.

We have found that lubricating oils refined by ordinary methods may berendered almost entirely resistant to sludge formation in heavy dutyservice for long periods of time by the incorporation therein of minoramounts of organic substituted dithiophosphates such as will bepresently described, together with minor amounts of an oilsolubleorganic sulfonate. Another advantage to be obtained by the use oforganic sulfonates with dithiophosphates is the solubilizing actionwhich the organic sulfonates exert on the dithiophossolubilized to asufficient degree for their effective use in lubricating oils with thehelp of small amounts of organic sulfonates.

Although some of the oil soluble organic sulfonates have previously beenadded to lubricating oils as anti-corrosion agents experience has shownthat on long continued heating in the presence of air they oxidize andbreak down to form sludge. As a result they will not effectively preventthe formation of undesirably large amounts of sludge under conditions ofextreme service. It is surprising therefore that the addition ofoil-soluble 'organic sulfonates to a lubricating oil compositioncontaining a dithiophosphate additive will further increase theresistance of the oil to sludge formation.

Among the various oil-soluble organic sulfonates which are effective toproduce improved anti-sludging properties in the oils of the presentinvention are the so-called petroleum or mahogany sulfonates, well-knownproducts of the oil industry. We prefer to employ the petroleumsulfonates on account of their availability and low cost. Otheroil-soluble organic sulfonates may, however, be employed. We may use,for example, the dialkyl sulfosuccinates such as the diamyl, dioctyl,dicapryl, diundecyl and dilauryl sulfosuccinates; also the alkylarylsulfonates such as diisobutyl naphthalene sulfonate, diisopropylnaphthalene sulfonate, lauryl phenyl sulfonate; the esters ofsulfophthalic acid such as the diamyl and dioctyl esters;lauryl-,S-sulfobutyrate which is an ester of a sulfomonocarboxylic acid;esters of sulfosebacic acid; capryl phenyl ether sulfonate; terpenylalkyl ether sulfonates; sulfonated esters of talloel fatty acids such asthe capryl ester; and the various sulfotricarballylates phates. Some ofthe dithiophosphates, for example di-(tert. amyl phenyl)dithiophosphate, which are diflicultly soluble in oil alone may be suchas triethylhexyl sodium sulfotricarballylate and others. We prefer touse these oil-soluble surface-active organic sulfonates in the form oftheir metal salts such as those of zinc, sodium, magnesium, potassium,etc., and, preferably, those of the alkaline earth metals, calcium,barium and strontium.

- The various dithiophosphates which we have found useful in improvinglubricating oils and which may be employed to advantage with theoil-soluble organic sulfonates just described are those having thegeneral formula in which R is a. member of the group consisting of aryl,alkyl, aralkyl, cycloalkyl, aryloxyalkyl,

acylaryl and alkoxyaryl radicals and M is hydrogen or a salt-formingradical and n is the .valence of M. More specifically, compounds of'dithiophosphate, dilauryl dithiophcsphate, di-

octadecyl dithiophosphate, etc. We prefer to use those dialkyldithiophosphates in which the alkyl group has from 5 to 30 carbon atomssince the longer alkyl chains tend to increase the solubility of thedithiophosphates in lubricating oils. The diaryl dithiophosphates andthe diaryl dithiophosphates in which the aryl group bears an alkyl,alkoxy or cycloaliphatic group are also useful such as for examplediphenyl dithiophosphate, di-(2,4-diamyl phenyl) dithiophosphate,dikeryl diphenyl dithiophosphate (a product obtained by treatingchlorinated kerosene with a phenol in th presence of aluminum chlorideand then reacting with P2S5) and the various di-(wax substituted diaryl)dithiophosphates as described in detail in our copending applicationSerial No. 415,411, filed October 17, 1941, to have the alky] group inthe alkaryl radical to have 5 to 30 carbon atoms so that the compoundsare more easily oil-soluble. We may also employ the dicycloaliphaticdithiophosphates such as those prepared by reacting cyclopentanol,cyclohexanol, cycloheptanol, and methyl, ethyl, propyl and amylsubstituted cyclopentanol, cyclohexanol and cycloheptanol, etc. withPass. Th diaryloxyalkyl dithiophosphates such as bi(2,4-diamylphenoxyethyl) dithiophosphate, the diacylaryl dithiophosphates such asdi-(lauroyl phenyl) dithiophosphate and the dialkoxyaryldithiophosphates may also be added to lubricating oils with oil-solubleorganic sulfonates to improve the sludging properties of the oil.

We prefer to employ these various organic substituted dithiophosphatesin the form of their metal salts, preferably the alkaline earth metalsalts. Among the various metal salts which may be employed are those ofthe salt-forming radicals nickel, aluminum, cadmium, tin, zinc, magnesium, calcium, strontium, barium and others.

The various dithiophosphates described above are employed by u in ourimproved lubricating oils, preferably in amounts ranging from 0.1 to 3%by weight. Smaller amounts, 0.05 to 1.0%, of the oil-soluble organicsulfonates may be employed with the dithiophosphates to prevent sludgeformation. The greater the tendency of the oil to form sludge the moreorganic sulionate should be employed. The amount of both of thesesubstituents in the oil will also depend to some extent upon the purposefor which the oil is intended. For example, an oil intended forextremely heavy duty service should contain more of both thedithiophosphate and the organic sulfonate as compared with the amountsrequired by an oil intended for ordinary usage.

The resistance of our improved lubricating oils to sludge formation wasdemonstrated by the following test. cc. samples of the oil to be testedwere heated at 330 F. in a 50 cc. open glass beaker for 24 hours. At theend of the heating period the oil samples were cooled and examined fordeposits of sludge. Under the conditions of this test conventionallyrefined lubricating oils, when containing certain dithiophosphateadditives, show formation of a heavy dark sediment. When testing solventrefined oils the sedimentis not as heavy which indicates that someconstituent in the oil tends to decompose under prolonged We also preferOil A-Mid-Continent, conventionally refined,

SAE 20-W Additive Results 1.07 barium diiauryl dithiophosphate--- Darksedime 1.0% barium dilauryl dithiophosphate N at 0.45 calcium petroleumsulionate 0 5e OiZ B--Pennsylvania, solvent refined, SAE 10-W AdditiveResults 1.0% barium diiauryl dithiophosphate--. Sediment. 1.0% bariumdilauryl dithiophos hate C} 0.2% dlal kyi benzene sodium sul onate..-1.0% bar um dilauryl dithiophosphatc. D 0.2% tri-(n-hexyl) sodiumsulfotricar- 1 giuglate' d 1 1 a h arium i aury it iophosphate..- Darksedim 1.5%; barium dllauryl dithio hospbate-.- C1 ent 0.35% calciumpetroleum su fonate 1.3% barium dlifllllyl ditbiophosphategioctyl sitliium 1silirilsuccinaule1 sum 1 aury it iophos ate.-. gg ya b d l g g gg }Very slight precipitate.

o ar um capry it 10p osphate... Heav reel 1 t 1.3% barium dicapryldithiophosphate--. v h p m e 0.2% dioctyl sodium suliosuccinate ery 5 lgt precipitate Oil C-Mid-Contiment, solvent-refined, SAE 10-W AdditiveResults 1.0% barium di-(2, 4-diam 1 hen 1 di- Sedim thiopbosphate. y p yent 1.0% barium di-(2, i-diamyl phenyl) dithiophosphate. Clear. 0.45%calcium petroleum suli'onate 1.0% bar um dioctyl dithiophosphate.Sediment. 1.0% barium dioctyl dithiophosphate- Cl 0.45% calciumpetroleum Suiionate 1.0% bar um d iauryl dithiophosphate. Sediment. 0.6%bar1um dilauryl dithiophosphate 0.1 didecyl calcium sulfosuccinate Whatwe claim is;

1. A hydrocarbon lubricating oil containing as an antioxidant andanticorrosive agent having a tendency to form sludge in the oil uponcontinued heating thereof 0.1-3% by weight of a dithiophosphate of theformula 2. A hydrocarbon lubricating oil containing as an antioxidantand anticorrosive agent having a tendency to form sludge in the oil uponcontinued heating thereof 0.1-3% by weight of a dithiophosphate of theformula in which R is a member of the group consisting of alkyl, aryl,aralkyl, cycloalkyl, aryloxyalkyl, acylaryl and alkoxyaryl radicals, Mis a.

".polyvalent metal and n .is the valence of M, said oil also containingas a sludge-inhibiting agent for said dithiophosphate 0.05-1% by weightof an oil-soluble petroleum sulfonate.

3. A hydrocarbon lubricating oil containing as an antioxidant andanticorrosive agent having a tendency to form sludge in the oil uponcontinued heating thereof 0.l-3% by weight of a dithiophosphate of theformula in which R is a hydrocarbon radical having 5-30 carbon atoms, Mis a polyvalent metal and n is the valence of M,- said oil alsocontaining as a sludge-inhibiting agent for said dithiophosphate 0.054%by weight of an oil-soluble petro-' leum sulfonate.

4. A hydrocarbon lubricating oil containing as an antioxidant andanticorrosive agent having a tendency to form sludge in the oil uponcontinued heating thereof 0.1-3% by weight of a dithiophosphate of theformula in which R is an alkaryl group, the alkyl groups of whichcontain 5-30 carbon atoms, M is a polyvalent metal and n is the valenceof M, said oil also containing as a sludge-inhibiting agent for saiddithiophosphate 0.05-1% by weight of an oilsoluble petroleum sulfonate.

5. A hydrocarbon lubricating oil containing as an antioxidant andanticorrosive agent having a tendency to form sludge in the oil uponcontinued 10 heating thereof 0.13% by weight of a polyvalent 20 alsocontaining as a sludge-inhibiting agent for said dithiophosphate 0.05-1%by weight of an oilsoluble organic sulfonate.

ELMER W. COOK. WILLIAM D. THOMAS, J R.

